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21.
Saul G. de Amorim Jean-Pierre Barthélemy Celso C. Ribeiro 《Journal of Classification》1992,9(1):17-41
We study the application of simulated annealing and tabu search to the solution of the clique partitioning problem. We illustrate
the effecveness of these techniques by computational results associated not only with randomly generated problems, but also
with real-life problems arising from applications concerning the optimal aggregation of binary relations into an equivalence
relation. The need for these approaches is emphasized by the example of a special class of instances of the clique partitioning
problem for which the most commonly used heuristics perform arbitrarily badly, while tabu search systematically obtains the
optimal solution.
Résumé Nous étudions dans cet article l'application du recuit simulé et de la méthode de recherche tabou dans la résolution du problème de partitionnement de graphes en cliques. Nous illustrons l'efficacité de ces techniques par des résultats numériques associés soit à des problèmes génerés au hasard, soit à des problèmes réels concernant l'agrégation de relations binaires dans une relation d'équivalence. L'intérêt de ces approches est mis en évidence à travers une classe de problèmes pour lesquels les heuristiques les plus connues ont une performance arbitrairement mauvaise, tandis que la méthode de recherche tabou obtient systématiquement des solutions optimales.相似文献
22.
Alard O Luguet A Pearson NJ Griffin WL Lorand JP Gannoun A Burton KW O'Reilly SY 《Nature》2005,436(7053):1005-1008
Abyssal peridotites are assumed to represent the mantle residue of mid-ocean-ridge basalts (MORBs). However, the osmium isotopic compositions of abyssal peridotites and MORB do not appear to be in equilibrium, raising questions about the cogenetic relationship between those two reservoirs. However, the cause of this isotopic mismatch is mainly due to a drastic filtering of the data based on the possibility of osmium contamination by sea water. Here we present a detailed study of magmatic sulphides (the main carrier of osmium) in abyssal peridotites and show that the 187Os/188Os ratio of these sulphides is of primary mantle origin and can reach radiogenic values suggesting equilibrium with MORB. Thus, the effect of sea water on the osmium systematics of abyssal peridotites has been overestimated and consequently there is no true osmium isotopic gap between MORBs and abyssal peridotites. 相似文献
23.
Jung A Maier R Vartanian JP Bocharov G Jung V Fischer U Meese E Wain-Hobson S Meyerhans A 《Nature》2002,418(6894):144
The genome of the human immunodeficiency virus is highly prone to recombination, although it is not obvious whether recombinants arise infrequently or whether they are constantly being spawned but escape identification because of the massive and rapid turnover of virus particles. Here we use fluorescence in situ hybridization to estimate the number of proviruses harboured by individual splenocytes from two HIV patients, and determine the extent of recombination by sequencing amplified DNA from these cells. We find an average of three or four proviruses per cell and evidence for huge numbers of recombinants and extensive genetic variation. Although this creates problems for phylogenetic analyses, which ignore recombination effects, the intracellular variation may help to broaden immune recognition. 相似文献
24.
运用薄层色谱扫描技术研究了回流温度时(76℃)1,2,3,4,6-五-O-乙酰基-β-D-吡喃半乳糖的超声溴化反应,通过测定反应液中初始物半乳糖的浓度随超声辐照时间的变化,采用一次法和初速度法分别建立了该反应的反应动力学方程:r=9.348×10-3ρ1(一次法),r0=1.07 8×10-2ρ1,0(初速度法),确认这一反应对初始物半乳糖为一级反应,探讨了可能的反应机理,根据推测的反应机理得到的动力学方程为r=Kρ1,(K=2k1k2ρNBS/k5),与实验结果一致. 相似文献
25.
For more than four decades, transistors have been shrinking exponentially in size, and therefore the number of transistors in a single microelectronic chip has been increasing exponentially. Such an increase in packing density was made possible by continually shrinking the metal-oxide-semiconductor field-effect transistor (MOSFET). In the current generation of transistors, the transistor dimensions have shrunk to such an extent that the electrical characteristics of the device can be markedly degraded, making it unlikely that the exponential decrease in transistor size can continue. Recently, however, a new generation of MOSFETs, called multigate transistors, has emerged, and this multigate geometry will allow the continuing enhancement of computer performance into the next decade. 相似文献
26.
Helias V Saison C Ballif BA Peyrard T Takahashi J Takahashi H Tanaka M Deybach JC Puy H Le Gall M Sureau C Pham BN Le Pennec PY Tani Y Cartron JP Arnaud L 《Nature genetics》2012,44(2):170-173
The human ATP-binding cassette (ABC) transporter ABCB6 has been described as a mitochondrial porphyrin transporter essential for heme biosynthesis, but it is also suspected to contribute to anticancer drug resistance, as do other ABC transporters located at the plasma membrane. We identified ABCB6 as the genetic basis of the Lan blood group antigen expressed on red blood cells but also at the plasma membrane of hepatocellular carcinoma (HCC) cells, and we established that ABCB6 encodes a new blood group system (Langereis, Lan). Targeted sequencing of ABCB6 in 12 unrelated individuals of the Lan(-) blood type identified 10 different ABCB6 null mutations. This is the first report of deficient alleles of this human ABC transporter gene. Of note, Lan(-) (ABCB6(-/-)) individuals do not suffer any clinical consequences, although their deficiency in ABCB6 may place them at risk when determining drug dosage. 相似文献
27.
Momozawa Y Mni M Nakamura K Coppieters W Almer S Amininejad L Cleynen I Colombel JF de Rijk P Dewit O Finkel Y Gassull MA Goossens D Laukens D Lémann M Libioulle C O'Morain C Reenaers C Rutgeerts P Tysk C Zelenika D Lathrop M Del-Favero J Hugot JP de Vos M Franchimont D Vermeire S Louis E Georges M 《Nature genetics》2011,43(1):43-47
Genome-wide association studies (GWAS) have identified dozens of risk loci for many complex disorders, including Crohn's disease. However, common disease-associated SNPs explain at most ~20% of the genetic variance for Crohn's disease. Several factors may account for this unexplained heritability, including rare risk variants not adequately tagged thus far in GWAS. That rare susceptibility variants indeed contribute to variation in multifactorial phenotypes has been demonstrated for colorectal cancer, plasma high-density lipoprotein cholesterol levels, blood pressure, type 1 diabetes, hypertriglyceridemia and, in the case of Crohn's disease, for NOD2 (refs. 14,15). Here we describe the use of high-throughput resequencing of DNA pools to search for rare coding variants influencing susceptibility to Crohn's disease in 63 GWAS-identified positional candidate genes. We identify low frequency coding variants conferring protection against inflammatory bowel disease in IL23R, but we conclude that rare coding variants in positional candidates do not make a large contribution to inherited predisposition to Crohn's disease. 相似文献
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29.
Résumé Nous montrons que Poincaré, dans son article de 1905, adopte un point de vue actif concernant le groupe des Transformations
de Lorentz. Ce point de vue, selon lequel les transformations agissent directement sur les systèmes physiques (sans toucher
au système de coordonnées), est naturel pour lui car il est celui des géomètres et aussi implicitement celui de Lorentz dans
son traitement mathématique des états correspondants. L'adoption de ce point de vue est même nécessaire pour corriger l'?
erreur ? de Lorentz dans sa définition d'un système globalement en mouvement. La contraction des longueurs, comme la dilatation
des temps, traditionnellement attachées aux changements de référentiels, trouvent également une explication physique relativiste
dans cette approche.
Présenté par J. D. Norton (Manuscrit re?u le 29 juillet 2005) Publication éléctronique le 14 mars 2006 相似文献
Présenté par J. D. Norton (Manuscrit re?u le 29 juillet 2005) Publication éléctronique le 14 mars 2006 相似文献
30.